The present invention relates in general to a portable refrigerator/heater unit for the storage and transport of temperature sensitive medical, biological and chemical material and, more particularly, to an electronically controlled portable refrigerator/heater unit for the storage and transport of temperature sensitive medical, biological and chemical material.
Medicants, such as bio-synthetic insulin and bio-synthetic human growth hormone, are temperature sensitive and should be transported and stored within a predetermined temperature environment. If such medicants become frozen, they may be damaged. If the temperatures at which such medicants are transported and stored exceed a predetermined range, they may lose their potency and may become toxic. Equipment heretofore employed for the transporting and storing of such medicants were not satisfactory because protection against freezing did not fulfill the requirements and, also, the temperature at which such medicants were subjected rose to unacceptable levels before arrival at the destination.
The patent to William E. Seaman, U.S. Pat. No. 5,320,162, issued on Jun. 14, 1994, for Single Pole Double Throw Thermostat For Narrow Range Temperature Regulation discloses a portable, thermally insulated storage and transport container for temperature sensitive material. Disposed within the container is a thermostat having a bimetalic strip actuating a single pole, double throw switch. In one position of the switch, temperature below a lower limit of a set point range is sensed. In the other position of the switch, temperature above an upper limit of the set point range is sensed. When the temperature in the container is above the upper limit of the set point range, a Peltier cooler is operated. When the temperature in the container is below the lower limits of the set point range, a heater is operated. A fan provides air flow and convection. In the cooling mode, the fan operates continuously. In the heating mode, the fan is not operated. Power input is provided through a jack which is connected to a 12-volt d.c. source. Connected to the jack is a filter that prevents possible spikes or transients from damaging electronic circuits and prevents radio frequency interference signals which could interfere with other operating equipment.
In the U.S. patent to Reed, U.S. Pat. No. 4,364,234, issued on Dec. 21, 1982, for Control Circuitry For Thermoelectric Environmental Chamber, there is disclosed an electronically controlled, temperature sensitive portable container that operates off a 12-volt battery. The temperature within the chamber of the portable container is maintained within a desired temperature range. A thermoelectric module is operated to heat or cool the environmental chamber for controlling the temperature within the environmental chamber. Operational amplifiers in conjunction with resistors produce the voltages that represent the upper and lower limit of the selected desired temperature.
The U.S. patent to Wills, U.S. Pat. No. 3,616,846, issued on Nov. 1, 1971, for Control System For Heating And/Or Cooling System discloses an electronic system for controlling the temperature within an office building, a home and the like. A bridge circuit provides both a reference voltage and a voltage representative of the temperature in an office building, a home and the like. Within the bridge circuit is a thermistor that changes its resistive value in relationship to the temperature of the environment. The output of the bridge circuit is applied to operational amplifiers. When the sensed temperature exceeds a predetermined magnitude, an operational amplifier changes its state to operate an electronic switch. This action, in turn, operates cooling equipment. When the sensed temperature falls below a predetermined magnitude, another operational amplifier changes its state to actuate another electronic switch. This action, in turn, operates heating equipment.